CODEWITHSUNDEEP
memorycpu-architecturememory-address
rollo123
rollo123

Reputation: 25

how to tell how many memory addresses a processor can generate

Let's say a computer can hold a word size of 26 bits, I'm curious to know how many memory addresses can the processor generate?

I'm thinking that the maximum number it can hold would be 2^26 - 1 and can have 2^26 unique memory addresses.

I'm also curious to know that if let's say that each cell in the memory has a size of 12 bits then how many bytes of memory can this processor address?

My understanding is that in most cases a processor can hold up to 32 bits which is 4 bytes and each byte is 8 bits. However, in this case, each byte would be 12 bits and the processor would be able to address 2^26/12 bytes of memory. Is that safe to say?

Upvotes: 0

Views: 703

Answers (1)

Erik Eidt
Erik Eidt

Reputation: 26656

I'm thinking that the maximum number it can hold would be 2^26 - 1 and can have 2^26 unique memory addresses.

I agree.  We usually refer to this as the size of the address space.

As for the next question:

These days, the term byte is generally agreed to means 8 bits, so 12 bits would mean 1.5 bytes.  It is a matter of terminology, though, which has varied in the long past.

So, I would say 226 12-bit words is capable of holding/storing 226 * 1.5 bytes, though they are not individually addressable, and would have to be packed & unpacked to access the separate bytes.

The DEC PDP-8 computer was a 12 bit computer and word addressable, so there were multiple schemes for storing characters: two 6 bit characters in a 12 bit word, and also 1 & 1/2 8-bit characters in a 12-bit word, so three 8-bit characters in two 12-bit words.

Similar issues occur when storing packed booleans in a memory, where each boolean takes only a single bit, yet the processor can access a minimum of 8 bits at a time, so must extract a single bit from a larger datum.

Upvotes: 1

Related Questions